The requirements on the error evaluation index for wind power prediction (WPP) and drawbacks of the traditional evaluation indexes are summarized. By distinguishing the influences on electric power reliability of a positive error from those of a negative error

a risk assessment index is proposed for WPP errors and its calculation. The risk assessment index is defined as an integration of the probability of a power disturbance event caused by WPP error and the losses caused by the event. Having a monetary dimension

the index can be accumulated as risk cost of WPP error with other costs directly. Thus

the confusion on how to trade off “ignoring the events of small probability” against “attaching importance to the events with heavy losses” can be dispelled for those events with big error as well as very small probability. Finally

an actual wind farm system in Ningxia

China is applied to illustrating the feasibility and availability of the risk index. This work is jointly supported by National Basic Research Program of China (973 Program) (No. 2013CB228204)

Australian Research Council Project (No. DP120101345)

NSFC-EPSRC Collaborative Project (No. NSFC-513111025-2013

No. EPSRC-EP/L001063/1)

and State Grid Corporation of China.